ambassador under president george w. bush says president obama has to decide now what his objectives are with syria, its government, and its stockpile of chemical weapons. >> the president said, himself, almost exactly a year ago, that the use of chemical weapons would cross a red line, and when a president of the united states makes a statement like that, he needs to be prepared to do something pretty dramatic if the red line is crossed. otherwise, his credibility is gravely damaged. i think that's where we are at the moment. >> reporter: the united nations disarmament chief arrived in syria today to press the syrian government to allow the u.n. investigative scene to go to the site of the reported chemical attack. greg? >> thank you. >>> celebrating the dream, then and now, thousands of americans descending on the national mall in washington marking 50 years since the historic civil rights march on washington and reverend dr. martin luther king's speech for the ages. we'll go live to the monument for more. doug? >> rep